Electrochemical fuel cell stack with improved reactant manifolding and sealing

ABSTRACT

An electrochemical fuel cell stack with improved reactant manifolding and sealing includes a pair of separator plates interposed between adjacent membrane electrode assemblies. Passageways fluidly interconnecting the anodes to a fuel manifold, and interconnecting the cathodes to an oxidant manifold, comprise at least one fluid passageway formed between adjoining non-active surfaces of the pairs of separator plates. The passageways extend through one or more ports penetrating the thickness of one of the plates thereby fluidly connecting the manifold to the opposite active surface of that plate, and the adjacent electrode. The ports comprise walls that have surfaces that are angled more than 0 degrees and less than 90 degrees with respect to the direction of fluid flow in the fluid passageway upstream of the port. During operation, electrochemical fuel cell stacks comprising fluid ports with angled walls benefit from reduced pressure loss. Turbulence, which is believed to have adverse effects on the membrane electrode assemblies of solid polymer fuel cells, is also reduced.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of U.S. patent application Ser. No.09/471,564 filed Dec. 23, 1999, now U.S. Pat. No. 6,232,008, which is acontinuation-in-part of U.S. patent application Ser. No. 09/116,270filed Jul. 16, 1998, now U.S. Pat. No. 6,066,409. The '270 applicationin turn relates to and claims priority benefits from U.S. ProvisionalPatent Application Ser. No. 60/052,713 filed Jul. 16, 1997. The '564 and'270 applications, and the '713 provisional application, areincorporated herein by reference in their entireties.

FIELD OF THE INVENTION

The present invention relates to electrochemical fuel cell stacks. Inparticular, the invention provides an electrochemical solid polymer fuelcell stack with improved reactant manifolding and sealing.

BACKGROUND OF THE INVENTION

Electrochemical fuel cells convert reactants, namely, fuel and oxidantfluid streams, to generate electric power and reaction products.Electrochemical fuel cells employ an electrolyte disposed between twoelectrodes, namely a cathode and an anode. The electrodes generally eachcomprise a porous, electrically conductive sheet material and anelectrocatalyst disposed at the interface between the electrolyte andthe electrode layers to induce the desired electrochemical reactions.The location of the electrocatalyst generally defines theelectrochemically active area.

Solid polymer fuel cells typically employ a membrane electrode assembly(“MEA”) consisting of a solid polymer electrolyte or ion exchangemembrane disposed between two electrode layers. The membrane, inaddition to being ion conductive (typically proton conductive) material,also acts as a barrier for isolating the reactant streams from eachother.

The MEA is typically interposed between two separator plates that aresubstantially impermeable to the reactant fluid streams. The plates actas current collectors and provide support for the MEA. Surfaces of theseparator plates that contact an electrode are referred to as activesurfaces. The separator plates may have grooves or open-faced channelsformed in one or both surfaces thereof, to direct the fuel and oxidantto the respective contacting electrode layers, namely, the anode on thefuel side and the cathode on the oxidant side. Such separator plates areknown as flow field plates, with the channels, which may be continuousor discontinuous between the reactant inlet and outlet, being referredto as flow field channels. The flow field channels assist in thedistribution of the reactant across the electrochemically active area ofthe contacted porous electrode. In some solid polymer fuel cells, flowfield channels are not provided in the active surfaces of the separatorplates, but the reactants are directed through passages in the porouselectrode layer. Such passages may, for example, include channels orgrooves formed in the porous electrode layer or may just be theinterconnected pores or interstices of the porous material.

In a fuel cell stack, a plurality of fuel cells are connected together,typically in series, to increase the overall output power of theassembly. In such an arrangement, an active surface of the separatorplate faces and contacts an electrode and a non-active surface of theplate may face a non-active surface of an adjoining plate. In somecases, the adjoining non-active separator plates may be bonded togetherto form a laminated plate. Alternatively both surfaces of a separatorplate may be active. For example, in series arrangements, one side of aplate may serve as an anode plate for one cell and the other side of theplate may serve as the cathode plate for the adjacent cell, with theseparator plate functioning as a bipolar plate. Such a bipolar plate mayhave flow field channels formed on both active surfaces.

The fuel stream that is supplied to the anode separator plate typicallycomprises hydrogen. For example, the fuel stream may be a gas such assubstantially pure hydrogen or a reformate stream containing hydrogen.Alternatively, a liquid fuel stream such as aqueous methanol may beused. The oxidant stream, which is supplied to the cathode separatorplate, typically comprises oxygen, such as substantially pure oxygen, ora dilute oxygen stream such as air.

A fuel cell stack typically includes inlet ports and supply manifoldsfor directing the fuel and the oxidant to the plurality of anodes andcathodes respectively. The stack often also includes an inlet port andmanifold for directing a coolant fluid to interior passages within thestack to absorb heat generated by the exothermic reaction in the fuelcells. The stack also generally includes exhaust manifolds and outletports for expelling the unreacted fuel and oxidant gases, as well as anexhaust manifold and outlet port for the coolant stream exiting thestack. The stack manifolds, for example, may be internal manifolds,which extend through aligned openings formed in the separator layers andMEAs, or may comprise external or edge manifolds, attached to the edgesof the separator layers.

Conventional fuel cell stacks are sealed to prevent leaks andinter-mixing of the fuel and oxidant streams. Fuel cell stacks typicallyemploy fluid tight resilient seals, such as elastomeric gaskets betweenthe separator plates and membranes. Such seals typically circumscribethe manifolds and the electrochemically active area. Applying acompressive force to the resilient gasket seals effects sealing.

Fuel cell stacks are compressed to enhance sealing and electricalcontact between the surfaces of the plates and the MEAs, and betweenadjoining plates. In conventional fuel cell stacks, the fuel cell platesand MEAs are typically compressed and maintained in their assembledstate between a pair of end plates by one or more metal tie rods ortension members. The tie rods typically extend through holes formed inthe stack end plates, and have associated nuts or other fastening meansto secure them in the stack assembly. The tie rods may be external, thatis, not extending through the fuel cell separator plates and MEAs,however, external tie rods can add significantly to the stack weight andvolume. It is generally preferable to use one or more internal tie rodswhich extend between the stack end plates through openings in the fuelcell separator plates and MEAs as, for example, described in U.S. Pat.No. 5,484,666. Typically springs, hydraulic or pneumatic pistons,pressure pads or other resilient compressive means are utilized tocooperate with the tie rods and end plates to urge the two end platestowards each other to compress the fuel cell stack components.

The passageways which fluidly connect each electrode to the appropriatestack supply and/or exhaust manifolds typically comprise one or moreopen-faced fluid channels formed in the active surface of the separatorplate, extending from a reactant manifold to the area of the plate whichcorresponds to the electrochemically active area of the contactedelectrode. In this way, for a flow field plate, fabrication issimplified by forming the fluid supply and exhaust channels on the sameface of the plate as the flow field channels. However, such channels maypresent a problem for the resilient seal, which is intended to fluidlyisolate the other electrode (on the opposite side of the ion exchangemembrane) from this manifold. Where a seal on the other side of themembrane crosses over open-faced channels extending from the manifold, asupporting surface is required to bolster the seal and to prevent theseal from leaking and/or sagging into the open-faced channel. Onesolution adopted in conventional separator plates is to insert a bridgemember that spans the open-faced channels underneath the resilient seal.The bridge member preferably provides a sealing surface that is flushwith the sealing surface of the separator plate so that a gasket-typeseal on the other side of the membrane is substantially uniformlycompressed to provide a fluid tight seal. The bridge member alsoprevents the gasket-type seal from sagging into the open-faced channeland restricting the fluid flow between the manifold and the electrode.Instead of bridge members, it is also known to use metal tubes or otherequivalent devices for providing a continuous sealing surface around theelectrochemically active area of the electrodes (see, for example, U.S.Pat. No. 5,570,281), whereby passageways, which fluidly interconnecteach electrode to the appropriate stack supply or exhaust manifolds,extend laterally within the thickness of a separator or flow fieldplate, substantially parallel to its major surfaces.

Conventional bridge members are affixed to the separator plates afterthe plates have been milled or molded to form the open-faced fluidchannels. One problem with this solution is that separate bridge membersadd to the number of separate fuel cell components that are needed in afuel cell stack. Further, the bridge members are typically bonded to theseparator plates, so care must be exercised to ensure that therelatively small bridge members are accurately installed and that thebonding agent does not obscure the manifold port. It is also preferableto ensure that the bridge members are installed substantially flush withthe sealing surface of the separator plate. Accordingly, theinstallation of conventional bridge members on separator plates addssignificantly to the fabrication time and cost for manufacturingseparator plates for fuel cell assemblies. Therefore, it is desirable toobviate the need for such bridge members, and to design anelectrochemical fuel cell stack so that the fluid reactant streams arenot directed between the separator plates and MEA seals.

SUMMARY OF THE INVENTION

In the present approach, passageways fluidly interconnecting an anode toa fuel manifold, or interconnecting a cathode to an oxidant manifold, inan electrochemical fuel cell stack are formed between the non-activesurfaces of a pair of adjoining separator plates. The passageway thenextends through one or more ports penetrating the thickness of one ofthe plates thereby fluidly connecting the manifold to the oppositeactive surface of that plate, and the contacted electrode. The portsthat penetrate the thickness of one of the plates, are angled ports,such that the fluid flowing from one side of plate to the opposite sideis not directed against any perpendicular surfaces. That is, thesurfaces of the ports are not perpendicular to the plane of the plates,but are angled and/or curved to reduce turbulence and pressure loss.

The non-active surfaces of adjoining separator plates in a fuel cellstack can thus cooperate to provide passageways for directing at leastone of the reactant from a respective fuel or oxidant manifold to theappropriate electrodes. In cases where the non-active surfaces of twoadjoining separator plates accommodate both the oxidant and fuelreactant streams, the fuel and oxidant reactant streams are, of course,fluidly isolated from each other. Coolant passages may also beconveniently provided between the non-active surfaces of adjoiningseparator plates.

In other words, the fluid port directs the fluid at an angle between 0degrees and 90 degrees from the direction of fluid flow in thepassageway directly upstream of the fluid path. In this disclosure, 0degrees is defined as being parallel to the direction of the fluid flowin the passageway upstream of the fluid port and 90 degrees is definedas being perpendicular to the direction of the fluid flow in thepassageway upstream of the fluid port. That is, the fluid port walls areshaped so that the fluid flow vectors are not directed against any wallsthat are angled more than 90 degrees from the fluid flow vector.Preferably the effective angle of the fluid port walls is between about20 degrees and about 45 degrees with respect to the direction of thefluid flow in the passageway upstream of the fluid port.

In a preferred embodiment, the non-active surfaces of adjoiningseparator plates provide fluid passageways for both the fuel and oxidantstreams, which are, of course, fluidly isolated from each other. Thatis, within the electrochemical fuel cell stack:

at least one of the fuel stream passageways traverses a portion of oneof the adjoining non-active surfaces of a pair of the separator plates,and the at least one fuel stream passageway comprises a fuel fluid portfluidly connecting a portion of the fuel stream passageway on thenon-active surface, with the active surface of one of the pair ofplates;

at least one of the oxidant stream passageways traverses a portion ofone of the adjoining non-active surfaces of a pair of the separatorplates, and the at least one oxidant stream passageway comprises anoxidant fluid port fluidly connecting a portion of the oxidant streampassageway on the non-active surface, with the active surface of theother of the pair of plates; and

the fuel fluid port and the oxidant fluid port each comprise walls thatare angled more than 0 degrees and less than 90 degrees with respect tothe direction of fluid flow in the respective fuel and oxidantpassageways upstream of the respective fluid port.

In preferred embodiments, to further reduce turbulence the fluid portwalls are curved. For example, the fluid port walls may be convex. Thefluid port walls may also be curved more than one direction. Forexample, the walls may be curved in both the in-plane and through-planedirections (wherein the “plane” is defined herein as the plane of theactive surface).

In one embodiment the angled fluid port is in the shape of an elongatedslot and is fluidly connected to a plurality of fluid channels formed inthe active surface.

In any of the above embodiments, the separator plates may be flow fieldplates wherein the active surfaces have reactant flow field channelsformed therein, for distributing reactant streams from the supplymanifolds across at least a portion of the contacted electrodes. In suchcases the angled fluid ports may fluidly connect passageways on thenon-active plate surfaces to reactant flow field channels on the activeplate surface.

Fuel cell separator plates incorporating the disclosed features may bemade from any materials that are suitable for fuel cell separatorplates. Preferred properties for fuel cell separator plate materialsinclude impermeability to reactant fluids, electrical conductivity,chemical compatibility with fuel cell reactant fluids and coolants, andphysical compatibility with the anticipated operating environment,including temperature and the humidity of the reactant streams. Forexample, carbon composites have been disclosed herein as suitablematerials. Expanded graphite composites may also be suitable materials.The disclosed discrete fluid distribution channels may be formed, forexample, by embossing a sheet of expanded graphite material. Compositeplate materials may further comprise a coating to improve one or more ofthe plate's desired properties. Persons skilled in the art willunderstand that the present separator plates may be made from othermaterials that are used to make conventional separator plates, such as,for example, metal.

When expanded graphite is the material selected for the separatorplates, the fluid ports, in addition to other features of the plate,such as, for example, the fluid passageways, and flow field channels,may be made by embossing a sheet of deformable expanded graphite. A pairof embossing dies may comprise features that cooperate with one anotherto form features such as the fluid ports. When a carbon composite is thematerial selected for the separator plates, the fluid ports and otherfeatures such as the flow field channels and non-active surfacepassageways may be molded.

The electrochemical fuel cell stack may optionally further comprisereactant exhaust manifolds for directing a reactant stream from one, orpreferably more, of the fuel cell electrodes. In preferred embodiments,reactant stream passageways fluidly interconnecting the reactant exhaustmanifolds to the electrodes also traverse a portion of adjoiningnon-active surfaces of a pair of separator plates and comprise angledexhaust ports fluidly connecting the non-active surface of the plates tothe respective active surfaces.

In further embodiments passages for a coolant may also be formed betweenco-operating non-active surfaces of adjoining anode and cathode plates,or one or more coolant channels may be formed in the active surface ofat least one of the cathode and/or the anode separator plates. In anoperating stack, a coolant may be actively directed through the coolingchannels or passages by a pump or fan, or alternatively, the ambientenvironment may passively absorb the heat generated by theelectrochemical reaction within the fuel cell stack.

As mentioned above, passageways for both the fuel and oxidant reactantstreams may extend between adjoining non-active surfaces of the samepair of plates, but the passageways are fluidly isolated from eachother. To improve the sealing around the reactant stream passagewayslocated between adjoining non-active surfaces of the separator plates,the fuel cell stack may further comprise one or more gasket sealsinterposed between the adjoining non-active surfaces. Alternatively, orin addition to employing gasket seals, adjoining separator plates may beadhesively bonded together. To improve the electrical conductivitybetween the adjoining plates, the adhesive is preferably electricallyconductive. Other known methods of bonding and sealing the adjoiningseparator plates may be employed.

In any of the embodiments of an electrochemical fuel cell stackdescribed above, the manifolds may be selected from various types ofstack manifolds, for example internal manifolds comprising alignedopenings formed in the stacked membrane electrode assemblies andseparator plates, or external manifolds extending from an external edgeface of the fuel cell stack.

As used herein, adjoining components are components that are in contactwith one another, but are not necessarily bonded or adhered to oneanother. Thus, the terms “adjoin” and “contact” are intended to besynonymous.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of the results of a vectoral flow analysis fora separator plate that comprises a fluid port with walls that areperpendicular to the direction of fluid flow in the passageway extendingfrom the manifold.

FIG. 2 is an illustration of the results of a vectoral flow analysis fora separator plate that comprises a fluid port with walls that are angledwith respect to the direction of fluid flow in the passageway extendingfrom the manifold.

FIG. 3 is a partial three-dimensional section view of a separator platethat comprises an angled fluid port.

FIG. 4 is a partial section view of two plates that may used asembossing dies or mold plates for forming the separator plate shown inFIG. 3.

FIG. 5A is a partial plan view of a separator plate that comprises afluid port in the shape of a slot.

FIG. 5B is a partial section view of the separator plate of FIG. 5A.

FIG. 6 is a partial three-dimensional view of a separator plate thatcomprises a fluid passage that fluidly connects the non-active andactive surfaces of the plate, wherein the fluid passage is curved in thethrough-plane and in-plane directions.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT(S)

FIG. 1 is an illustration of the results of a vectoral flow analysisthat depicts the flow vectors of a fluid that is directed from manifold10, through passageway 20 on one side of a separator plate (not shown),through port 30, and then to channel 40 on the opposite side of theseparator plate. In FIG. 1, the bold, solid lines are indicative of theoutline of the flow passageway. The bold, broken lines in FIG. 1 areindicative of some, but not all, of the transverse edges of thepassageway. In this analysis, passageway 20 corresponds, for example, toa passageway associated with the non-active surface of the separatorplate, and channel 40 corresponds, for example, to a channel associatedwith the active surface of the separator plate. In the example of FIG.1, port 30 comprises walls that are substantially perpendicular to themajor substantially planar surfaces of the separator plate. That is, thewalls of port 30 are oriented substantially 90 degrees with respect tothe direction of fluid flow in passageway 20.

Known fuel cell separator plates (not shown) that employ bridges andfluid passageways extending from manifolds to flow field channels on theactive surface of the separator plate provide a substantially straightfluid path. That is, the fluid path is substantially parallel to theplane of the active surface, and substantially laminar flow is expectedin the passageway between the manifold and the fluid flow field area.Accordingly, the effect of turbulence between the fluid manifolds andthe flow field area was not a concern with fuels cells using separatorplates with this design.

For fuel cell separator plates providing a fluid path like the one shownin FIG. 1, turbulence may be a concern because the turbulence results inincreased pressure losses. In addition, in solid polymer fuel cellsemploying “perpendicular” ports like port 30, the fluid exiting port 30typically impinges directly on the electrode and enters directly intothe active area where turbulence may have an adverse effect on theelectrode and membrane electrolyte. In particular, empirical data showsthat the portions of the membrane opposite ports like port 30 arelocations where degradation of the membrane is more likely to occur.

FIG. 2 is an illustration of the results of a vectoral flow analysisthat depicts the flow vectors of a fluid that is directed from amanifold (not shown), through passageway 50 on one side of a separatorplate (not shown), through angled port 60, and then to channel 70 on theopposite side of the separator plate. In this analysis, passageway 50corresponds, for example, to a passageway associated with the non-activesurface of the separator plate, and channel 70 corresponds, for example,to a channel associated with the active surface of the separator plate.In the example of FIG. 2, port 60 comprises walls that are curved andare angled more than 0 degrees and less than 90 degrees with respect tothe direction of fluid flow in passageway 50. In the example of FIG. 2,the effective angle of port 60, with respect to the direction of fluidflow in passageway 50 is about 30 degrees. A comparison of the resultsdepicted in FIGS. 1 and 2 demonstrates a much-reduced amount ofturbulence that was unexpected given the thickness of typical fuel cellseparator plates. To reduce the weight and volume of fuel cell stacks,separator plates are generally made thin. For example, typical fuel cellseparator plates are less than 5 millimeters thick. Accordingly, theoffset is typically small between the passageway (for example,passageway 50) and the flow field channel (for example, channel 70)which are both formed within the thickness of the plate (that is, on thenon-active surface and the active surface, respectively).

FIG. 3 is a partial three dimensional sectional view of separator plate100. The reactant fluid flows generally in the direction of arrow 110,from a passageway 120, through port 130 and into channel 140. The wallsof port 130 are angled with respect to the direction of fluid flow inpassageway 120 by an angle of about 20 degrees. Further, the walls ofport 130 are curved in the through plane direction in a convex shape toprovide a sturdier leading edge that is less susceptible to damage.

FIG. 4 is a partial section detail view of two embossing dies or moldplates that may be employed in cooperation with each other to form anangled port like port 130 in FIG. 3. For example, in the case whereplates 150 and 160 are embossing dies, a compressible formable materialsuch as, expanded graphite, is placed between plates 150 and 160. Whenplates 150 and 160 are pressed together, raised portion 155, forexample, forms passageway 120 and half of port 130, and raised portion165 forms channel 140 and the other half of port 130. Alternatively,when plates 150 and 160 are mold plates, the plates are pressed togetherand then the uncured plate material is injected into the mold, fillingthe void spaces. The uncured plate material is then cured in the mold.After curing, plates 150 and 160 are separated, releasing a molded platecomprising features like those of the plate illustrated in FIG. 3.

FIG. 5A is a partial plan view of separator plate 200, which comprisesfluid manifold 210 and flow field area 220 which comprises reactantchannels 230. Fluid is directed from manifold 210 to channels 230 viafluid passageway 240 on the opposite surface of the plate (shown in thepartial section view in FIG. 5B) and angled fluid port 250 (shown inboth FIGS. 5A and 5B). Separator plate 200 further comprises grooves 260and 270 for accommodating seals for fluidly isolating manifold 210 andflow field area 220. Section line B—B, in FIG. 5A, indicates thelocation of the section view shown in FIG. 5B. In this example, fluidport 250 is in the shape of an elongated slot that is fluidly connectedto a plurality of channels 230.

In the embodiment illustrated in FIG. 6, separator plate 300 comprisespassageway 310, fluid port 320, and flow field channel 330. In thisembodiment, fluid port 320 curves in both the through-plane directionand the in-plane direction. Like other embodiments disclosed herein,fluid passageway 310, fluid port 320, and flow field channel 330 may allbe formed by embossing dies or plates, similar to those shown in FIG. 4.

While particular elements, embodiments and applications of the presentinvention have been shown and described, it will be understood, ofcourse, that the invention is not limited thereto since modificationsmay be made by those skilled in the art without departing from the scopeof the present disclosure, particularly in light of the foregoingteachings.

What is claimed is:
 1. A fuel cell stack comprising: (a) a plurality ofmembrane electrode assemblies each comprising an anode, a cathode and anion exchange membrane interposed between said anode and cathode; (b) apair of separator plates interposed between adjacent pairs of saidplurality of membrane electrode assemblies, said pair of separatorplates comprising: an anode plate having an active surface contactingsaid anode and an oppositely facing non-active surface, and a cathodeplate having an active surface contacting said cathode and an oppositelyfacing non-active surface adjoining said non-active surface of saidanode plate; (c) at least one reactant stream passageway traversing aportion of said non-active surface of at least one of said separatorplates; and (d) a fluid port fluidly connecting said portion of saidpassageway on said non-active surface with said active surface of saidseparator plate.
 2. The fuel cell stack of claim 1 wherein said activesurface comprises at least one channel fluidly connected to said fluidport.
 3. The fuel cell stack of claim 1 wherein said fluid port is inthe shape of an elongated slot and is fluidly connected to a pluralityof fluid channels formed in said active surface.
 4. The fuel cell stackof claim 1 wherein said separator plate is molded and said fluid port isformed by a mold.
 5. The fuel cell stack of claim 1 wherein saidseparator plate is embossed and said fluid port is formed by a raisedfeature on an embossing die.
 6. The fuel cell stack of claim 1 whereinsaid portion of said reactant stream passageway that traverses saidnon-active surface of said separator plate comprises a groove formed insaid separator plate.
 7. The fuel cell stack of claim 1 furthercomprising coolant passages formed in said non-active surface of saidseparator plate.
 8. The fuel cell stack of claim 1 further comprisingcoolant passages formed in said active surface of said separator plate.9. The fuel cell stack of claim 1 further comprising an internalmanifold opening therein, wherein said portion of said reactant streampassageway that traverses said non-active surface of said separatorplate is fluidly connected to said manifold opening.
 10. The fuel cellstack of claim 1 wherein said fluid port comprises walls that are angledmore than 0 degrees and less than 90 degrees with respect to thedirection of fluid flow in said passageway upstream of said fluid port.11. The fuel cell stack of claim 10 wherein said fluid port compriseswalls that are angled more than about 20 degrees and less than about 45degrees with respect to the direction of fluid flow in said passagewayupstream of said fluid port.
 12. The fuel cell stack of claim 10 whereinsaid fluid port comprises walls that are angled about 20 degrees withrespect to the direction of fluid flow in said passageway upstream ofsaid fluid port.
 13. The fuel cell stack of claim 10 wherein said fluidport comprises walls that are angled about 45 degrees with respect tothe direction of fluid flow in said passageway upstream of said fluidport.
 14. The fuel cell stack of claim 10 wherein said fluid port wallsare curved to reduce turbulence within said fluid port.
 15. The fuelcell stack of claim 14 wherein at least one of said fluid port walls isconvex.
 16. The fuel cell stack of claim 14 wherein said fluid portwalls are curved both in the in-plane and through-plane directions, andwherein said plane is the plane of said active surface.
 17. A fuel cellseparator plate comprising: (a) an active surface; (b) an oppositelyfacing non-active surface; (c) an internal reactant supply manifoldopening formed in said non-active surface; (d) at least one reactantstream supply channel formed in said non-active surface, said supplychannel fluidly connected to said supply manifold opening and traversinga portion of said non-active surface of said separator plate; (e) afluid supply port fluidly connecting said supply channel with saidactive surface of said separator plate; (f) an internal reactant exhaustmanifold opening formed in said active surface; (g) at least onereactant stream exhaust channel formed in said non-active surface, saidexhaust channel fluidly connected to said exhaust manifold opening andtraversing a portion of said non-active surface of said separator plate;and (h) a fluid exhaust port fluidly connecting said exhaust channelwith said active surface of said separator plate.
 18. The separatorplate of claim 17 wherein each of said supply and exhaust ports comprisewalls that are angled more than 0 degrees and less than 90 degrees withrespect to the direction of fluid flow in the channel upstream ofrespective said port.
 19. A fuel cell separator plate comprising: (a) ananode plate having an active surface and an oppositely facing non-activesurface; (b) a cathode plate having an active surface and an oppositelyfacing non-active surface adjoining said non-active surface of saidanode plate; and (c) wherein at least one of said fuel and oxidantstream channels also traverses a portion of said adjoining non-activesurfaces of said anode and cathode plates and wherein said at least oneof said fuel and oxidant stream channels comprises a fluid port fluidlyconnecting said portion of said channel on said non-active surface withsaid active surface of one of said pair of separator plates.
 20. Thefuel cell plate of claim 19 wherein said fluid port comprises walls thatare angled more than 0 degrees and less than 90 degrees with respect tothe direction of fluid flow in said passageway upstream of said fluidport.
 21. The fuel cell plate of claim 20 wherein said fluid portcomprises walls that are angled more than about 20 degrees and less thanabout 45 degrees with respect to the direction of fluid flow in saidpassageway upstream of said fluid port.
 22. The separator plate of claim20 wherein said fluid port comprises walls that are angled about 20degrees with respect to the direction of fluid flow in said passagewayupstream of said fluid port.
 23. The separator plate of claim 22 whereinsaid adjoining non-active surfaces are bonded together using anelectrically conductive adhesive.
 24. The separator plate of claim 20wherein said fluid port comprises walls that are angled about 45 degreeswith respect to the direction of fluid flow in said passageway upstreamof said fluid port.
 25. The separator plate of claim 20 wherein saidfluid port walls are curved to reduce turbulence within said fluid port.26. The separator plate of claim 25 wherein at least one of said fluidport walls is convex.
 27. The separator plate of claim 25 wherein saidfluid port walls are further curved in both the in-plane andthrough-plane directions, and wherein said plane is the plane of saidactive surface.
 28. The fuel cell plate of claim 19 further comprisingcoolant passages formed between cooperating non-active surfaces of saidanode and cathode plates.
 29. The separator plate of claim 19 whereinsaid adjoining non-active surfaces of said anode plate and said cathodeplate are bonded together.
 30. An electrochemical fuel cell stackcomprising: (a) a plurality of membrane electrode assemblies eachcomprising an anode, a cathode, and an ion exchange membrane interposedbetween said anode and cathode; (b) a pair of separator platesinterposed between adjacent pairs of said plurality of membraneelectrode assemblies, said pair of separator plates comprising: an anodeplate having an active surface contacting said anode, and an oppositelyfacing non-active surface, and a cathode plate having an active surfacecontacting said cathode, and an oppositely facing non-active surfaceadjoining said non-active surface of said anode plate; (c) a fuel supplymanifold for directing a fuel stream to at least one of said anodes; (d)an oxidant supply manifold for directing an oxidant stream to at leastone of said cathodes; and (e) fuel and oxidant stream passagewaysfluidly connecting said fuel and oxidant supply manifolds to at leastone of said anodes and at least one of said cathodes, respectively,wherein at least one of said fuel and oxidant stream passagewaystraverses a portion of said adjoining non-active surfaces of a pair ofsaid separator plates and said at least one passageway comprises a fluidport fluidly connecting said portion of said passageway on saidnon-active surface with said active surface of one of said pair ofseparator plates.
 31. The electrochemical fuel cell stack of claim 30wherein passages for a coolant are formed between cooperating non-activesurfaces of a pair of said separator plates.
 32. The electrochemicalfuel cell stack of claim 30 wherein, for each of said pairs of separatorplates, said adjoining non-active surfaces of said anode plate and saidcathode plate are bonded together.
 33. The electrochemical fuel cellstack of claim 32 wherein said adjoining non-active surfaces are bondedtogether using an electrically conductive adhesive.
 34. Theelectrochemical fuel cell stack of claim 30 wherein said at least one ofsaid fuel and oxidant stream passageways comprise open-faced channelsformed in said non-active surface of one plate of said pair of separatorplates.
 35. The electrochemical fuel cell stack of claim 30 wherein saidat least one of said fuel and oxidant stream passageways compriseopen-faced channels formed in the non-active surfaces of both plates ofsaid pair of separator plates.
 36. The electrochemical fuel cell stackof claim 30 further comprising an oxidant exhaust manifold for directingan oxidant stream from at least one of said cathodes wherein an oxidantstream passageway fluidly interconnecting said oxidant exhaust manifoldto a cathode traverses a portion of adjoining non-active surfaces of apair of said separator plates.
 37. The electrochemical fuel cell stackof claim 30 further comprising a fuel exhaust manifold for directing afuel stream from at least one of said anodes wherein a fuel streampassageway fluidly interconnecting said anode exhaust manifold to ananode traverses a portion of adjoining non-active surfaces of a pair ofsaid separator plates.